Backyard Biogas

by Marilyn Anthony

Thirteen-year-old Clayton Young, a home-schooled Berks County teen, is working to design a solution that would enable small-scale biodigesters to provide year-round cooking gas in Syrian refugee camps. But when he first brought the lofty idea to his mother, Jennifer, she was adamantly opposed. “We’re not doing a project on poop,” she told him.

Biodigesters combine raw or cooked food waste, animal or human fecal matter and water in an anaerobic (oxygenless) environment to produce three essential byproducts: liquid fertilizer, methane-based cooking gas and rich soil. Learning more about the process was a perfect opportunity for Clayton to complete an assigned science project to solve a real world problem.

He’s since won his mother over.

The pair are now working with the global Solar CITIES program, based in Chester County, which trains trainers to introduce this simple biogas technology into resource-poor communities and other places lacking sufficient public health infrastructure—including refugee camps.

Thomas Culhane, a research scientist in urban planning, environmental analysis and policy, is a co-founder of the organization. He believes biodigester systems, whose simple technology requires little more than plastic cubes and tubes, can turn dangerous waste into an asset. He says a biodigester converts waste into soil in three to six days—instead of three to six months of composting. The clean gas that is produced requires no additional refining to be usable, and it also creates nutrient-dense fertilizer in just 24 hours. Using up the food waste helps reduce the greenhouse gases that would be produced if it rotted in a landfill. The process extracts the last bit of photosynthetic energy from the food waste and converts it to cooking fuel. A next generation design uses mirrors to direct solar energy to the units to keep them warm in winter.

As Solar CITIES vice president and co-founder Janice Kelsey puts it, “We’re able to deal with food and manure at its source.” Biodigester technology on an industrial scale is already in use in countries such as Germany and Sweden. Culhane and Kelsey’s efforts center on the construction of“appliance-sized” digesters for home use.

Kelsey uses a portion of her suburban Chester County backyard as a demonstration area for what she affectionately refers to as her “pet dragon,” since it “breathes fire.” Inside a plastic-wrapped greenhouse are two 1,000-gallon intermediate bulk-shipping containers. Plastic piping directs some gas from the containers to capacious storage bags in the greenhouse and some to a countertop stove in Kelsey’s kitchen. Her “baby dragon” produces about four hours of cooking gas daily. Kathy Puffer, a Solar CITIES board member with a home digester in the Hudson Valley, refers to the liquid fertilizer byproduct as “Compeaujolais,” and applies it to her gardens, lawn and indoor vegetable growing system.

In December 2014, Solar CITIES member and neighbor Jody Spangler installed “Gassy Girl,” the largest residential biogas system in the U.S. on her Windy Hill Farms in East Nantmeal Township. With Kelsey, Spangler tirelessly promotes biodigesters to school and community groups. This spring Solar CITIES will collaborate with Villanova University on a multidisciplinary project to build and analyze small-scale biodigesters.

Culhane says the enthusiastic response his ideas received from Pennsylvania Amish and Mennonite communities, educators, off-grid innovators and activists for social justice led him to select Chester County as the Solar CITIES headquarters. This enthusiasm is evident even from the once reluctant Jennifer Young as she reflects on her son Clayton’s project.

“The most important thing he is learning is how something we can do in our backyard can help other people.”